1. Technical Field
The present invention relates to a calibration device for measuring the maximum pull force developed by a banding tool while tightening a metal band about a tubular sleeve; which includes a force release assembly for gradually releasing the force to prevent damage to the force sensing element.
2. Description of the Prior Art
Various tools are known in the art for terminating a metal band about a tubular sleeve, to secure, for example, an electrical cable shield, such as a woven copper braid, to an electrical connector housing. In order to prevent damage to the tubular sleeve on the connector housing, often made of cast aluminum, various banding tools are known having a preset pull force to avoid damage to the tubular sleeve on the electrical connector housing. For example, both a power operated tool and a manually operated tool are known which have assemblies which prevent the tools from applying more than a predetermined amount of pull force. These tools are assigned to the same assignee of the present invention and are disclosed in copending applications Ser. No. 07/277,325, filed on Nov. 29, 1988, and Ser. No. 07/370,597, filed on Jun. 23, 1989.
A calibration device is generally used to measure the maximum pull force generated by both the manually operated tool and the power operated tool. Known calibration devices for such tools often include a strain gauge assembly and a pair of releasable jaws for holding a portion of a metal band. In order to calibrate the tool, one end of a metal band is placed into the releasable jaws on the calibration device. The other end of the metal band is placed into the tool. The tool is then operated and the maximum pull force is read off a dial on the calibration device. In some power operated tools, the driving motor, whether electrical or pneumatic, is reversible. With such tools the driving motor may be operated in reverse to gradually relieve the force on the force sensing element within the strain gauge assembly. In other power operated tools and known manually operated tools, there are no means to gradually reduce the force on the force sensing element after the maximum pull force has been determined. With such tools, the band is cut between the tool and the calibration device. However, such cutting results in a sudden release of force which can damage the force sensing element. Replacement of damaged force sensing elements can be rather costly.
Another problem with known calibration devices is that it is necessary for the banding tool to be stationary with respect to the calibration device during calibration. This requires that the nosepiece of the tool be held in intimate contact with the calibration device. In known calibration devices, the contour of the nosepiece of the tool is molded into the frame of the calibration device. However, since different banding tools have different nosepiece configurations, such calibration devices can only be used for banding tools with the same nose-piece configuration.